C++ - 随机数生成器(random-number generator) 的 详解 及 代码

随机数生成器(random-number generator) 的 详解 及 代码

 

本文地址: http://blog.csdn/caroline_wendy/article/details/17322165

 

随机数, C语言的函数是rand(), C++则是随机数生成器(random-number generator) = 分布对象(distribution object) + 引擎(engine);

使函数每次生成不同的随机数, 需要使用静态(static)局部变量, 这样分布对象和引擎就能保持(hold)状态(state), 每次都生成一个新的;

生成随机的整数, 使用分布对象uniform_int_distribution<>, 默认模板参数是int;

生成随机的浮点数, 使用分布对象uniform_real_distribution<>, 默认模板参数是double;

 

代码:

 

#include <iostream>
#include <vector>
#include <string>
#include <random>


using namespace std;

std::vector<unsigned> good_randVec()
{
	static std::default_random_engine e; //静态
	static std::uniform_int_distribution<unsigned> u(0,9); //静态
	std::vector<unsigned> ret;
	for(size_t i=0; i<10; ++i)
		ret.push_back(u(e));
	return ret;
}

int main()
{
	std::default_random_engine e;
	std::cout << "engine : ";
	for(size_t i=0; i<10; ++i)
		std::cout << e() << " ";
	std::cout << std::endl;

	std::cout << "uniform : ";
	std::uniform_int_distribution<unsigned> u(0, 9); //即[0, 9]
	for(size_t i=0; i<10; ++i)
		std::cout << u(e) << " ";
	std::cout << std::endl;

	std::cout << "min : " << e.min() << " max : " << e.max() << std::endl;

	std::vector<unsigned> v1(good_randVec());
	std::vector<unsigned> v2(good_randVec());
	for(size_t i=0; i<v1.size(); ++i)
		std::cout << v1[i] << " ";
	std::cout << std::endl;
	for(size_t i=0; i<v2.size(); ++i)
		std::cout << v2[i] << " ";
	std::cout << std::endl;

	std::uniform_real_distribution<double> ud(0, 1);
	std::cout << "float : ";
	for(size_t i=0; i<10; ++i)
		std::cout << ud(e) << " ";
	std::cout << std::endl;

	return 0;
}

输出:

 

 

engine : 16807 282475249 1622650073 984943658 1144108930 470211272 101027544 1457850878 1458777923 2007237709 
uniform : 3 5 8 0 0 5 6 0 3 0 
min : 1 max : 2147483646
0 1 7 4 5 2 0 6 6 9 
3 5 8 0 0 5 6 0 3 0 
float : 0.686773 0.930436 0.526929 0.653919 0.701191 0.762198 0.0474645 0.328234 0.75641 0.365339